Why does browser send requests for static files?

Question

I have seen in Firebug that my browser sends requests even for all static files. This happened when I have enabled caching for static files. I also saw the server response with 304 status code.

Now, my question: Why should the browser send requests for all static files when the cache is enabled?

Is there a way that the browser does not send any request for static files until the expiration of the cache?

Answer 1

Browsers still send requests to the server in case the files are cached to get to know whether there are new contents to fetch. Note that the response code 304 comes from the server telling the browser that the contents it has cached are still valid, so it doesn't have to download them again.